Layer‑by‑layer biointerface engineering of biopolymer-nanoparticle hybrid coatings for durable antifouling and...

The layer-by-layer (LbL) assembly method using nanomaterials and naturally derived cationic and anionic polysaccharides is an actively researched field, driven to meet the demand for eco-friendly antifouling coatings and to improve current available alternatives. In this work, we present a strategy involving the activation of a polyethylene substrate to construct a four-layered coating consisting of an alginate-iron oxide nanoparticle hybrid (layer 1), bacterial cellulose (layer 2), an alginate-zinc sulfide nanoparticle hybrid (layer 3), and a protease extracted from Penaeus vannamei shrimp waste immobilized on graphene oxide nanosheets (layer 4). This assembly was deposited onto the polyethylene substrate using a polyethyleneimine adhesive sublayer via LbL self-assembly. The time required to deposit the layers in the optimal pH was measured using a design of experiments approach, which was based on atomic force microscopy and contact angle measurements. Our results indicate that layers 1 and 4 maintained their antifouling performance over time, due to the stability and low solubility of iron oxide nanoparticles and graphene oxide nanosheets. Moreover, we show that enhanced contact among each constructed layer progressively improved antifouling efficacy against bacterial adhesion (Escherichia coli and Staphylococcus aureus) and microalgal attachment (Nannochloropsis oculata). Our findings unequivocally indicate that the substantial water-binding capacity of biopolymers such as alginate and cellulose enables the fabrication of highly impermeable multilayer coatings when hybridized with nanoparticles. Overall, this study provides a straightforward and scalable approach for preparing antifouling and antimicrobial coatings from natural materials, aimed at significantly reducing biofilm growth and fouling in medical and marine applications.